Left: Number fraction of selected elements of HE 1518 (blue points) compared to the He-sdO [CW83] 0904 − 02 from Schindewolf et al. (2018) (red diamonds), the C/O-sdO UCAC4 108 − 030787 (green squares) from Werner et al. (2025), and the extreme helium star LSS 99 (violet pentagons) from Jeffery et al. (1998). The downward pointing arrows indicate the upper limits we estimated for HE 1518. Right: Same as the left plot, but the number fractions are shown relative to solar values.